Load balancing mechanisms are used in industry, such as the automotive industry, to permit movement and manipulation of heavy loads with only a minimal amount of manual force being provided by an operator. The load balancing mechanism typically is part of a material handling unit that includes a movable arm arrangement connected thereto which extends outwardly from an upright support column and is able to support a heavy load, such as an automotive component, on the end thereof. The load balancing mechanism includes a pneumatic cylinder arrangement which vertically supports the weight of the load but permits manual raising and lowering and sideward swivelling of the arm by a user. Since the cylinder arrangement effectively balances the entire weight of the load, only a minimal amount of manual force is required for movement of the heavy loads. Such load balancing mechanisms are known and used in numerous applications and industries.
A load balancing mechanism generally is connected between a support column and an arm assembly. The arm assembly is pivotally connected at one end to the support column to permit upward and downward pivoting of the arm assembly, while the opposite end of the arm assembly supports a load, the weight of which is balanced by a load-balancing cylinder assembly.
FIGS. 2 and 3 illustrate one type of a conventional arm assembly 19 that includes an inner bracket which connects to a support column such as support column 12 in a known manner. An outer bracket 21 also is provided to support a load such as a tool and/or an article being supported by the tool. Each of the inner and outer brackets 20 and 21 are formed the same in that they both include rigid pin supports 23 and 24 which have horizontal bores 25 and 26 respectively which extend horizontally therethrough. Each pin support 23 and 24 includes a vertically spaced pair of the bores 25 or 26, respectively, such that the arm assembly 19 defines a parallelogram double-arm arrangement.
This arm assembly 19 further includes a pair of vertically spaced apart elongate support arms 29, the upper one of which is illustrated in FIGS. 2 and 3. The opposite ends of the support arm 29 include generally U-shaped support yokes 30 and 31. Each of the support yokes 30 and 31 includes a spaced apart pair of support flanges 32 which each have a bore 33 extending horizontally therethrough. Each support yoke thereby has a pair of bores 33 which are adapted to be coaxially aligned with the opposite open ends of a corresponding one of the bores 25 or the bores 26.
To pivotally connect the support yokes 30 and 31 to the inner and outer brackets 20 and 21, a pivot pin arrangement is provided. In particular, a hollow cylindrical sleeve bearing 35 is press fit into each opposite open end of the bores 25 and 26 and their respective pin supports 23 and 24. Each sleeve bearing 35 is mechanically press-fitted into the bores 25 and 26 so as to pivotally support pivot pins 37 and 38 therethrough. The pivot pins 37 and 38 are secured in place by a keeper. The pivot pins 37 also extend outwardly from the bores 25 and 26 and are rotatably received in a corresponding pair of bores 33, such that the support yokes 30 and 31 of each arm 19 is pivotally connected at its opposite ends to the inner and outer brackets 20 and 21 respectively. The support arms 19 therefore are movable vertically about horizontal pivot axes 40 defined by the pivot pins 37 and 38.
To maintain the support flanges 32 of the yokes 30 and 31 away from the opposing surfaces of the inner and outer brackets 20 and 21, additional thrust bearings 39 are provided in the spaces between the pin supports 23 and 24 and the flanges 32 of the yokes 30 and 31 as seen, for example, in FIG. 3.
While this arrangement provides suitable pivot connections between the inner and outer brackets 20 and 21 and the intermediate support arms 29, it is difficult to replace the sleeve bearings 33. In particular, to replace a worn sleeve bearing 33, it is necessary to unload the unit and remove tooling therefrom, disassemble the arm assembly 19, take the parts to a shop area, and then mechanically remove the sleeve bearings 33 from their respective bores 25 or 26 typically by a press. Often, this procedure requires use of heavy equipment such as a forklift or the like.
The inventive load balancing mechanism 10 of FIGS. 1 and 4-8 overcomes the disadvantages of the prior art arrangement of FIGS. 2 and 3. In particular, the load balancing mechanism of the invention includes a readily removable bearing arrangement which does not require disconnection of the individual arms of the arm assembly, or disconnection of the cylinder assembly from the arm assembly.
Preferably, each arm assembly includes a yoke at the opposite ends thereof. Each yoke includes a pair of support flanges disposed on opposite sides of the respective support brackets for the support column and the load. Pivot pins are provided to pivotally connect the opposite ends of the support arm to the inner and outer brackets respectively.
However, a separate independently removable bearing arrangement is provided between each end of the pivot pin and the support flange. More particularly, the bearing arrangement at one end of a pivot pin is removable separately and independently from the bearing arrangement at the opposite end of the pin such that one bearing arrangement can be disassembled, removed and replaced without requiring disconnection of the bearing assembly at the opposite end of the same pivot pin. Thus, the pivot pin continues to support the support arm as each bearing assembly is individually removed and replaced. The arm assembly therefore does not need to be disconnected from the cylinder assembly or the support column as the bearing assemblies are changed. This greatly minimizes the time and difficulty in replacing worn bearings.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.